Infertility affects an estimated 2.4 million couples in the United States alone. Implantation failure may compromise fertility in as many as 20% of these couples, and effects even higher percentages of women with recurrent pregnancy loss. Preliminary data suggest that integrins, a family of cell adhesion molecules, participate in endometrial structure and function. These glycoproteins are present in the membranes of cells as heterodimeric alpha and beta subunits. The temporal and spatial expression of certain integrin receptor subunits are regulated during the menstrual cycle and preliminary studies suggest that these proteins are involved in endometrial receptivity. Specifically, we believe one integrin, alphav beta3, may be involved in the initial attachment of the embryo to the endometrial epithelium. The initial goal of this proposal is to prospectively map the expression of integrins in the normal endometrium throughout the menstrual cycle using immunohistochemistry and in situ hybridization, with special attention to those subunits that change their level of expression during the endometrial cycle. Using normal cycles as controls, we will then examine the distribution of integrins in women with luteal phase deficiency (LPD), recurrent pregnancy loss, an unexplained infertility. In addition the profile of integrins in stimulated cycles (with human menopausal gonadotropins) will be explored, as such medications have been reported to contribute to inadequate luteal phase endometrium. The vitronectin receptor subunit, Beta3, is expressed on epithelial cells during mid luteal phase and binds ligands known to be present on the developing trophoblast. This integrin subunit appears to be delayed in patients with disorders of endometrial maturation. Endometrial biopsies from infertility patients with LPD will be evaluated for the presence or absence of this cycle-specific integrin. The utility of this test as an inununohistochemical assay for the diagnosis luteal phase dysfunction will be determined. A third goal will be to determine what factors regulate integrin expression in normal endometrium. We will use an in vitro cell culture model of human endometrium (normal and transformed cells) to study the action of sex steroids, growth factors and the effects of mesenchyme (paracrine effects) and extracellular matrix on integrin expression. Using a series of proteins including steroid receptors, integrins and other cell specific markers, a fourth objective will be to develop a working reconstruction of endometrium, in vitro, to study the function of integrins in endometrial cells. Functionality studies will involve co-culture experiments to study endometrial/trophoblast interaction. A model of trophoblast-endometrial interaction is proposed and potential methods are presented to test the hypothesis that integrin-integrin interaction between endometrium and embryo forms the basis for cell-specific recognition and interaction, and defines the window of implantation.